Nginx缓存设置未生效，求助排查问题原因

Hey there, let's walk through the most common reasons your Nginx cache isn't kicking in even when you modify tst.txt—I've debugged tons of these issues, so here's where to start checking:

• Missing or incorrect cache directives in your location block
  You might have set up proxy_cache_path, but forgotten to enable caching in the target location with proxy_cache mycache; (replace mycache with your keys_zone name). Also, double-check proxy_cache_valid: if you set it to 0 or no-cache, Nginx won't store any cache. For example, a valid rule would look like:

  location /tst.txt {
      proxy_cache mycache;
      proxy_cache_valid 200 1h; # Cache 200 OK responses for 1 hour
  }
  

• Cache-control headers overriding Nginx settings
  If the origin server sends Cache-Control: no-cache, no-store or an Expires header set to a past timestamp, Nginx will respect these and skip caching. You can override this with proxy_ignore_headers Cache-Control Expires; if you want to force caching regardless of origin headers.

• Permission issues on the cache directory
  Nginx runs under a specific user (usually nginx or www-data). If your cache directory is owned by root and doesn't have read/write permissions for the Nginx user, it can't create cache files. Run these commands to verify:

  ls -ld /path/to/your/cache/dir # Check directory permissions
  ps aux | grep nginx # Find the user Nginx runs as
  

  Fix it with chown -R nginx:nginx /path/to/your/cache/dir (adjust user/group as needed).

• You didn't reload/restart Nginx after changing config
  It's easy to forget—after modifying your cache settings, you need to apply them with:

  nginx -s reload
  

  If you skipped this, Nginx is still using the old config without caching enabled.

• Problematic cache key configuration
  If your proxy_cache_key includes variable request data (like $http_cookie or $http_user_agent), every request might generate a unique cache key. That means even for the same tst.txt, Nginx stores multiple cache copies, making it look like caching isn't working. Stick to a simple key like $scheme$proxy_host$request_uri unless you need variation.

• Testing method is misleading
  Your browser might be using its own local cache, so you're not actually hitting Nginx's cache. Test with curl and check response headers for clues:

  curl -I http://your-domain/tst.txt
  

  Look for X-Cache: HIT (if you added add_header X-Cache $upstream_cache_status; to your config) or the Age header, which shows how long the cache has been stored.

• Cache path misconfiguration
  Check your proxy_cache_path settings:

  • max_size might be full, so Nginx can't add new cache files.
  • inactive might be set too short (e.g., 1m), so cache gets purged almost immediately after being stored.
  • levels might be incorrectly set, leading to Nginx failing to create the directory structure for cache files.

• Location rule isn't matching your request
  Maybe your location block (e.g., location /tst.txt) is being overridden by a more specific or higher-priority location (like a location ~* \.txt$ that doesn't have caching enabled). Use nginx -T to print your full config and verify which location is handling the tst.txt request.

• Nginx version compatibility issues
  Older Nginx versions (pre-1.1.12) had limited support for some cache features. If you're running a really old version, upgrading might fix the problem. Check your version with nginx -v.

内容的提问来源于stack exchange，提问作者NarūnasK